As mentioned in the article "L'allegement des chassis de bogies mecano-soudes des TGV" [Reducing the weight of all-welded bogie frames for TGVs], published in "La Revue Generale des Chemins de Fer", November 1992, pages 17 to 23, by the publishing house Gautier-Villars, a bogie performs a certain number of major functions by means of members that are designed and dimensioned for that purpose.
These functions are, in particular:
a guidance function, associated with the wheels and the axles; PA1 a braking function, associated with brake cylinders and disks; PA1 a traction function, associated with motor-and-gear-box units and with motor axles; PA1 a comfort function, associated with primary and secondary suspensions. PA1 said elements are one-piece elements; and PA1 said one-piece elements are made of a material containing, for the most part, an aluminum alloy. PA1 the aluminum alloy parts or elements are forged or cast and/or machined; and PA1 the aluminum alloy parts or elements are welded, screwed, glued, and/or riveted together. PA1 said elements 1 to 6 are one-piece elements; and PA1 said one-piece elements 1 to 6 are made of a material containing, for the most part, an aluminum alloy. PA1 some of the parts or of said one-piece elements 1 to 6 are obtained by a forging method and the others by a casting method; PA1 the one-piece elements obtained by a forging method are the one-piece elements that are subjected to the greatest stresses, and the one-piece elements obtained by a casting method are the one-piece elements of complex shape and subjected to smaller stresses; and PA1 the one-piece elements obtained by a forging method are obtained by a stamping method or by an extrusion method.
The art of a frame designer is to provide an architectural choice that achieves a suitable compromise between all of the various requirements taken into consideration, namely: resistance to fatigue; available space; mass; manufacturing costs.
State of the art bogie frames are mainly made of all-welded construction on the basis of A42 FP type steel sheet, as specified in French standard NF A 36-205.
The steel sheet is cut, shot-blasted, dressed, folded, and prepared for being assembled together by welding so as to form box-shaped subassemblies which, in a final assembly operation, are built up to constitute the final frame.
In addition to requiring a manufacturing cycle that is lengthy due to assembling together a large number of pieces of metal sheet, amounting to about 100 unit-pieces, the manufacture of the frame requires welding to be thoroughly mastered with respect both to performance and inspection.
From that article, and also from prior art bogies, it can be seen that studies on how to make bogie frames have been directed essentially to using steel, and in particular sheet steel.